Blasting cap



Jan. 31, was. BARAB 1 1,895,438

BLASTING CAP Filed July 18, 1951 Patented Jan. 31, 1933 JACOB BARAB, OF WILMINGTON, DELAWARE, ASSIGNOB '1'0 HERCULES POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE BLAs'rme car Application filed July 18,

My invention relates to improvement in blasting caps and more particularly to the provision of means whereby accidental firing of a cap through contact of the lead wires with a source of current will be positively avoided.

It is well known that blasting caps comprise a container'or casing in which an.explosive charge, as for example, fulminate of mercury, is contained. Extending into the casing is a pair of lead wires, the ends of which within the casing are connected by means of a bridge wire embedded in the ex: plosive charge or in a more readily fired initiating charge. The lead wires in their extension from the cap, and ordinarily they extend some four feet or more, are'mainly insulated, but their end portions are left .bare of insulation in order that they may be connected into a firing circuit. 7

It has been well recognized that the uninsulated end portions of the lead wires afford an opportunity for accidental discharge of the cap, since in carrying caps totheir point of use, for example, in a mine, the lead wires are frequently trailed and-are likely to become connected with a live circuit, as a trolley wire, or the like, or to receive a stray current by contact, for example, with a rail.

H-eretofore various means have been provided for avoiding accidental discharge of caps through inadvertent contact of the bare ends of the lead wires with a live circuit or source of stray current. It has, for example, been suggested to twist the bare ends of the lead wires together for a distance in order to short-circuit them and various devices have been provided for connecting the bare ends of the lead wires or securing them in contact 40 with one another with a view'to effecting a short-circuit.

The various means heretofore suggested for the avoidance of inadvertent firing of caps have not proven satisfactory for various reasons. Where the bare ends of the lead wires are twisted together for a distance, it is necessary in order for the twist to be reasonably efiective that it be'extended to the insulated portions of the wire and desirably even beyond. The twisted ends are disadvantage- 1931. Serial No. 551,635.

ous, since before the cap .can be used the ends must be untwisted and the untwisted ends being deformed and kinked are in an undesirable condition for making an efficient connection with a firing circuit. a

The various devices for connecting the lead wires or for holding the lead wires in electric contact with one another have been found relatively insecure, or if secure, extremely difficult to remove.

Now, in accordance with my invention, I provide means whereby inadvertent firing of blasting caps is effectively prevented and whereby the uninsulated ends of the lead wires may be prepared for connection into a firing circuit without eflort and, as is more important, without any distortion or kinking of the ends of wires.

' In accordance with this invention a protector formed of any desired conductive material, as for example, a conductive metal and of such'a structure is provided as to be readily attachable to the lead. wires to afford efli cient protection and, at the same time, be readily removed when it is desired to use the cap.

Having indicated in a general way the nature and purpose of this invention, I will pro-' ceed to a detailed description of -a preferred embodiment thereof with reference to the accompanying drawing in which:

Figure 1 is a perspective view of a blasting cap embodying this invention.

Figure 2 is a sectional view on line 2-2 Figure 1. V

Figure 3 is a view showing a modification of the invention as shown in Figure 1.

In the several views A indicates a casing, of any suitable material, as for example, o

copper, such as is usual in blasting caps. Within the casing is positioned the usual detonating charge adapted to be fired electrically through the medium of a fusible wire connected across the ends of lead wires B, C

within the casing. I The open end of the casing is suitably sealed as indicated at d. The lead wires B. C are insulated except for a distance from their free ends, as indicated at e,

l f. The uninsulated free end portions of the .groove and may be of any suitable or desired diameter. If desired, the member G may be solid rather than of ring form and may, if desired, be other than substantially circular. That is to say, it may be polygonal or partly straight sided and partly curved, etc., etc.

In practice the cap is protected until desired for use by wrapping the uninsulated free end portions e, f of the lead wires B, (I about the member G. As indicated in Figure 2, the lead wires will lie in the peripheral groove in member G and may be extended partially around the member as shown in Figure 1, or completely around as-shown in Figure 3.

Where the member G is provided with a peripheral groove having one wall h higher than the other, the wall 72. may be crimped or bent over the wires to retain them, especially where they are extended only partially about the member, as in Figure 1, rather than completely around the member, as in Figure 3. Where the high wall It is provided, it may be bent over the wires even though they are extended completely around the member and where the high wall it is not provided the walls of the peripheral groove, or one of them may be crimped in to hold the wires in any event.

The member G is desirably placed close up to the ends of the insulation on wires B, C and where the uninsulated portions of the wires are engaged with the member the cap will be protected since any current enterin the free ends of the lead wire will be shunte by member G and will not be effective to fire the cap.

Where it is desired to use the cap, the member G may be readily removed by holding the member and drawing off the wires. The end portions 6, f ofthe wires when drawn ofi or away from member G will be straight and without kinks and in condition for the making of an efiicient connection into a firing circuit.

What I claim ters Patent is;

1. In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a conducting member provided with a peripheral groove the uninsulated endportions of the lead wires as a pair being extended about said'member within said groove. 2. In combination with a blasting cap and desire to protect by Letadapted for electrical firing and provided with lead wires having uninsulated end portions, a conducting member provided with a peripheral groove engaged with the uninsulated end portions of the lead wires as a pair, a wall of said groove being crimped to retain said wires in said groove.

' 3. In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a conducting member provided with a peripheral groove engaged with the uninsulated end portions of the lead wires, one wall of said groove being higher than the other, the uninsulated end portions of said lead wires being extended about said member within said groove and said higher wall being crimped over said wires to retain them in said groove.

4. In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a conducting member provided with a peripheral groove, said member being positioned adjacent the 'end of the insulation on said wires and the uninsulated end portions thereof as a' pair being extended complete- ,ly about said member within said groove.

5. In. combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulatcd end portions, a conducting member provided with a peripheral groove engaged with the uninsulated end portions of the lead wires, the end portions of the lead wires being disposed in said groove so as to effect a contact between them per se.

6. In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a circular conducting member provided with a groove about its periphery, the end portions ofvthe lead wires being engaged in said groove.

7. In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a circular conducting member provided with a groove about its periphery, the end portions of the lead wires being disposed in said groove so as to eifect a contact between them per se.

In testimony of which invention, I have hereunto set my hand, at l/Vilmington,.Delaware, on this 14th day ofJuly, 1931.

- JACOB BAR-AB. 

